A Janus‐Headed Lewis Superacid: Simple Access to, and First Application of Me₃Si‐F‐Al(OR^F)₃

Abstract

Upon reaction of gaseous Me3SiF with the in situ prepared Lewis acid Al(OR(F))3, the stable ion-like silylium compound Me3 Si-F-Al(OR(F))3 1 forms. The Janus-headed 1 is a readily available smart Lewis acid that differentiates between hard and soft nucleophiles, but also polymerizes isobutene effectively. Thus, in reactions of 1 with soft nucleophiles (Nu), such as phosphanes, the silylium side interacts in an orbital-controlled manner, with formation of [Me3Si-Nu](+) and the weakly coordinating [F-Al(OR(F))3](-) or [((F)RO)3Al-F-Al(OR(F))3](-) anions. If exchanged for hard nucleophiles, such as primary alcohols, the aluminum side reacts in a charge-controlled manner, with release of FSiMe3 gas and formation of the adduct R(H)O-Al(OR(F))3. Compound 1 very effectively initiates polymerization of 8 to 21 mL of liquid C4 H8 in 50 mL of CH2 Cl2 already at temperatures between -57 and -30 °C with initiator loads as low as 10 mg in a few seconds with 100% yield but broad polydispersities.

Rapid, Low-Temperature Synthesis of Germanium Nanowires from Oligosilylgermane Precursors

“…According to 29 Si NMR spectroscopy of the solution phase containing TOPO, the peak from precursor 1 at -5.7 ppm vanished ( Figure S1, see Supporting Information) and a peak at 6.9 ppm appeared ( Figure S12, see Supporting Information), which can be assigned to hexamethyldisiloxane. 28 This change suggestrs that the free trimethylsilyl (TMS) groups of the precursor reacted with oxygen atoms and were trapped in the solution phase. As the reaction was performed under nitrogen atmosphere with degassed solvents, TOPO can be regarded as the main source of oxygen.…”

The Ion‐Like Supersilylium Compound tBu3Si–F–Al[OC(CF3)3]3

“…Soft nucleophiles, such as phosphanes PR 3 [5] By contrast, hard nucleophiles, such as primary alcohols ROH (e.g. R = tBu, tBuMe 2 Si), [5] react with the aluminum side, which leads to the release of Me 3-SiF and the formation of adduct R(H)OAl[OC(CF 3 ) 3 ] 3 . [5] In addition, it was also found that 2b polymerizes isobutene effectively.…”

“…The structural features of 2a were compared with those of its methyl-substituted congener Me 3 Si-F-Al[OC(CF 3 ) 3 ] 3 (2b). [4,5] In addition, the relative acidity …”

Elusive Silane–Alane Complex [SiH⋅⋅⋅Al]: Isolation, Characterization, and Multifaceted Frustrated Lewis Pair Type Catalysis

“…It is worth noting that such as econdary intermolecular interaction is also present in PhF·Al(OC(CF 3 ) 3 ) 3 (Al···F: 2.770(8) ), [10] . [18] In the present case,E t 3 SiH, as aw eak LB,i sn ot electron-donating enough to effectively stabilize the unsolvated Al(C 6 F 5 ) 3 so it seeks for additional stabilization by interacting with afluorine atom from asecond molecule.Incomparison, the geometry at the Al center in the F-bridged complex, [Et 3 SiÀF···Al(C 6 F 5 ) 3 ], features more pronounced pyramidalization, with aS i-F distance of 1.725 (2) , an Al···F contact of 1.841 (2) , and a AE C-Al-C of 348.18 8,a ll of which are averaged from three independent molecules (see Figure S22 in the Supporting Information).…”

“…[10] Interestingly,the fluorosilane adduct [Me 3 Si À F···Al{OC(CF 3 ) 3 } 3 ]was viewed as aJ anus-like bifunctional LA with as oft electrophilic Si site and ah ard electrophilic Al site for different substrates. [18] We hypothesized that, as ar esult of the demonstrated superior Lewis acidity and activity in many catalytic reactions by the alane compared to the borane,Al(C 6 F 5 ) 3 could lead to the isolable and characterizable simple silane-alane complex [R 3 Si À H···Al(C 6 F 5 ) 3 ], and thus uncover its potentially unique catalytic utilities.Inthis context, we communicate herein the isolation and structural characterization of silane-alane complexes with ah ydride or fluoride bridge.E xcitingly,t he silane-alane complex effectively catalyzes (or is involved in) avariety of transformations,including four different types of catalytic reactions:l igand redistribution of silanes,p olymerization of polar alkenes,h ydrosilylation of unactivated alkenes,and hydrodefluorination of fluoroalkanes.…”